Granulocyte blood cells. Light micrograph of two types of granulocytes, a type of white blood cell (leucocyte). At left is a neutrophil, with an eosinophil at right. Granulocytes, like all white blood cells, are part of the body's immune system. They are involved in the body's immune response, and contain granules with enzymes used to destroy pathogens. The surrounding cells are mostly red blood cells.